Co-sensitization Of Different TiO₂Film Electrodes With CdS,Bi₂S₃Quantum Dots And N719in Dye-sensitized Solar Cells

Dye-sensitized solar cell (DSSC) has attracted much research interests because it has excellent properties, such as low production cost, simple assemble technology, and low environmental impact. Currently, a solar cell consists of three main components:a sensitized photoanode which is typically a dye-sensitized nanocrystalline TiO2film electrode, an electrolyte solution and a counter electrode. Nanocrystalline TiO2film is an ideal photoanode material, due to the high energy conversion efficiency, long-term stability and low cost production. However, it is well known that the large band gap of TiO2limits its absorption to the ultraviolet region. Therefore, we must overcome the drawback to meet the requirements for practical applications. In this work, we have co-sensitized the different TiO2film electrodes with quantum dots (QDs) and dye N719, in an attempt to further improve the performance of DSSCs. The comparison of the properties between pure dye-sensitized and co-sensitized TiO2film electrodes is also investigated. The main contents and results could be summarize as follows:(1) The TiO2film electrodes sensitized with CdS QDs via chemical bath deposition method were successfully prepared as the photoanode of dye-sensitized solar cells (DSSCs). Microstructural characterizations by XRD, SEM, TEM and EDX show that the CdS nanocrystals with the cubic structure have intimate contact to the TiO2films. The amount of CdS QDs can be controlled by varying the dipping time. The experiment results demonstrate that the CdS QDs-sensitized solar cells show a wider absorption in the solar spectrum and an enhanced surface photovoltage response. The maximal photoelectric conversion efficiency of5.57%was achieved by the DSSC based on CdS QDs-sensitized TiO2film with4min. The performance improvement is ascribed to the enhancement of electron transport, the reduction of electron recombination and the long electron lifetime.(2) TiO2double layer films composed of TiO2hollow spheres as overlayer and TiO2nanoparticles as underlayer were prepared, and Bi2S3quantum dots have been successfully synthesized by hydrothermal method. Then the TiO2double layer films co-sensitized by Bi2S3QDs and N719dye were used as photoanode in dye-sensitized solar cells. The photoelectric properties of the DSSCs, with and without Bi2S3QDs adsorption were studied. The results shows that the η of TiO2/Bi2S3DSSCs is enhanced with the increasing of Bi2S3QDs amount in TiO2film and reaches up to7.50%when sensitization time of Bi2S3QDs arrives at10min. The performance improvement is ascribed to the higher light harvesting, and the reduction of electron recombination as well as the enhancement of electron transport with the introduction of Bi2S3QDs.